notes: chapter 9 (part 2): glycolysis & krebs cycle (9.2 & 9.3)
TRANSCRIPT
NOTES:Chapter 9
(Part 2): Glycolysis & Krebs Cycle(9.2 & 9.3)
● CELLULAR RESPIRATION: reactions in living cells in which sugars are
broken down and energy is released
Glucose + oxygen carbon dioxide + water + ENERGY
C6H12O6 + 6O2 6CO2 + 6H2O + energy
Mitochondria in a Liver Cell!!
● Food (glucose), like fuel, is “burned” by our cells for energy; however if it is burned all at once, too much energy is released.
● So, the reaction is broken down into many small steps controlled by ENZYMES
● the energy is transferred to the bonds of ATP which stores and releases the energy in usable amounts (packets) to be used by the cell
Recall: the ATP cycle
-Glucose = “large denomination” ($100)
-ATP = “small change” ($1)
*For each molecule of glucose, the cell can make approximately 36-38 ATP.
Steps of Cellular Respiration: Phase of
Resp.Occurs where?
Starts with?
Ends with?
# of ATP made
Glycoly-
sis
cyto-plasm
Krebs cycle
(Citric Acid Cyc)
E.T.C. (Resp
Chain) & oxidative phosphor
1 glucose
2 pyruvate; NADH
2
Steps of Cellular Respiration: Phase of
Resp.Occurs where?
Starts with?
Ends with?
# of ATP made
Glycoly-
sis
cyto-plasm
Krebs cycle
(Citric Acid Cyc)
inner matrix of mito-chondria
2 pyruvate
4 CO2,NADH,FADH2
E.T.C. (Resp
Chain) & oxidative phosphor
1 glucose
2 pyruvate; NADH
2
2
Steps of Cellular Respiration: Phase of
Resp.Occurs where?
Starts with?
Ends with?
# of ATP made
Glycoly-
sis
cyto-plasm
Krebs cycle
(Citric Acid Cyc)
inner matrix of mito-chondria
2 pyruvate
4 CO2,NADH,FADH2
E.T.C. (Resp
Chain) & oxidative phosphor
1 glucose
cristae(innermemb.of mito.)
NADH,FADH2,O2
2 pyruvate; NADH
H2O,
ATP
2
2
32-34(approx.)
1) oxidative phosphorylation: ● mode of ATP synthesis powered by redox reactions which transfer electrons from FOOD OXYGEN (occurs at the electron transport chain, or e.t.c.)
2 Modes of ATP Synthesis
2) Substrate-level phosphorylation:
● involves the enzyme-catalyzed transfer of inorganic phosphate from a molecule to ADP to form ATP.
● mode of ATP synthesis occurring in: -glycolysis (2 ATP) -Krebs cycle (2 ATP)
GLYCOLYSIS:
= “splitting of sugar”
Summary of Glycolysis:1 Glucose 2 pyruvate
2 ADP + 2 Pi 2 ATP(via substrate-level phosphorylation!)
2 NAD+ 2 NADH
Glycolysis occurs in 10 steps:
#1-5: energy-investment phase (2 ATP)
#6-10: energy-payoff phase (4 ATP)
NET GAIN OF 2 ATP!
Energy investment phase
Glucose
2 ATP used2 ADP + 2 P
4 ADP + 4 P 4 ATP formed
2 NAD+ + 4 e– + 4 H+
Energy payoff phase
+ 2 H+2 NADH
2 Pyruvate + 2 H2O
2 Pyruvate + 2 H2O
2 ATP
2 NADH + 2 H+
Glucose
4 ATP formed – 2 ATP used
2 NAD+ + 4 e– + 4 H+
Net
Glycolysis Citricacidcycle
Oxidativephosphorylation
ATPATPATP
Glucose
ATP
ADP
Hexokinase
ATP ATP ATP
Glycolysis Oxidationphosphorylation
Citricacidcycle
Glucose-6-phosphate
Glucose
ATP
ADP
Hexokinase
ATP ATP ATP
Glycolysis Oxidationphosphorylation
Citricacidcycle
Glucose-6-phosphate
Phosphoglucoisomerase
Phosphofructokinase
Fructose-6-phosphate
ATP
ADP
Fructose-1, 6-bisphosphate
Aldolase
Isomerase
Dihydroxyacetonephosphate
Glyceraldehyde-3-phosphate
2 NAD+
Triose phosphatedehydrogenase
+ 2 H+
NADH2
1, 3-Bisphosphoglycerate
2 ADP
2 ATPPhosphoglycerokinase
Phosphoglyceromutase
2-Phosphoglycerate
3-Phosphoglycerate
2 NAD+
Triose phosphatedehydrogenase
+ 2 H+
NADH2
1, 3-Bisphosphoglycerate
2 ADP
2 ATPPhosphoglycerokinase
Phosphoglyceromutase
2-Phosphoglycerate
3-Phosphoglycerate
2 ADP
2 ATPPyruvate kinase
2 H2OEnolase
Phosphoenolpyruvate
Pyruvate
GLYCOLYSIS ANIMATION!
KREBS CYCLE:
● glycolysis releases <1/4 of energy in glucose
● the majority remains in the 2 pyruvate
● IF molecular O2 is present: pyruvate enters a
mitochondrion, where enzymes of the KREBS CYCLE (a.k.a. the CITRIC ACID CYCLE) complete oxidation
BUT FIRST….
● Before the Krebs Cycle can begin, pyruvate must be converted to acetyl CoA, which links the cycle to glycolysis
But FIRST:
2 Pyruvate 2 acetyl CoA
This conversion occurs in 3 steps:
1) carboxyl group removed & given off as CO2
(2 CO2 produced, 1 for each pyruvate)
2) each remaining 2-C fragment is oxidized forming acetate; the extracted electrons are transferred to NAD+, forming NADH
(2 NADH produced, 1 for each fragment).
Final step of pyruvate acetyl CoA step:
3) Coenzyme A (from vitamin B) is attached to acetate acetyl CoA…
…on to the Krebs Cycle for further oxidation!
CYTOSOL
Pyruvate
NAD+
MITOCHONDRION
Transport protein
NADH + H+
Coenzyme ACO2
Acetyl Co A
Krebs Cycle (a.k.a. Citric Acid Cycle): ● 2 molecules of acetyl CoA enter the cycle (in
the matrix of a mitochondrion) & each combine with a molecule of OXALOACETATE…
● For EACH molecule of acetyl CoA that enters:
2 molecules of CO2 are given off
3 molecules of NADH are formed
1 molecule of FADH2 is formed
1 molecule of ATP formed by substrate phosphorylation (direct transfer of Pi to ADP from an intermediate substrate)
Pyruvate(from glycolysis,2 molecules per glucose)
ATP ATP ATP
Glycolysis Oxidationphosphorylation
CitricacidcycleNAD+
NADH
+ H+
CO2
CoA
Acetyl CoACoA
CoA
Citricacidcycle
CO22
3 NAD+
+ 3 H+
NADH3
ATP
ADP + P i
FADH2
FAD
● The Krebs Cycle has eight steps, each catalyzed by a specific enzyme;
● The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate;
● The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle!
● The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain.
ATP ATP ATP
Glycolysis Oxidationphosphorylation
Citricacidcycle
Citricacidcycle
Citrate
Isocitrate
Oxaloacetate
Acetyl CoA
H2O
ATP ATP ATP
Glycolysis Oxidationphosphorylation
Citricacidcycle
Citricacidcycle
Citrate
Isocitrate
Oxaloacetate
Acetyl CoA
H2O
CO2
NAD+
NADH
+ H+
-Ketoglutarate
CO2NAD+
NADH
+ H+SuccinylCoA
ATP ATP ATP
Glycolysis Oxidationphosphorylation
Citricacidcycle
Citricacidcycle
Citrate
Isocitrate
Oxaloacetate
Acetyl CoA
H2O
CO2
NAD+
NADH
+ H+
-Ketoglutarate
CO2NAD+
NADH
+ H+SuccinylCoA
Succinate
GTP GDP
ADP
ATP
FAD
FADH2
P i
Fumarate
ATP ATP ATP
Glycolysis Oxidationphosphorylation
Citricacidcycle
Citricacidcycle
Citrate
Isocitrate
Oxaloacetate
Acetyl CoA
H2O
CO2
NAD+
NADH
+ H+
-Ketoglutarate
CO2NAD+
NADH
+ H+SuccinylCoA
Succinate
GTP GDP
ADP
ATP
FAD
FADH2
P i
Fumarate
H2O
Malate
NAD+
NADH
+ H+
Oxaloacetate makes this a CYCLE!(&, P.S., it is my #7 most favorite term in bio!)
● SO, since 2 molecules of acetyl CoA go through the cycle, the “totals” are:
4 CO2
6 NADH
2 FADH2
2 ATP formed
